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Infinispan core module
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package org.infinispan.commands;

import org.infinispan.commons.util.Util;
import org.infinispan.context.InvocationContext;

import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

/**
 * The core of the command-based cache framework.  Commands correspond to specific areas of functionality in the cache,
 * and can be replicated using the {@link org.infinispan.remoting.rpc.RpcManager}
 *
 * @author [email protected]
 * @author Manik Surtani
 * @since 4.0
 */
public interface ReplicableCommand {
   /**
    * Performs the primary function of the command.  Please see specific implementation classes for details on what is
    * performed as well as return types. Important: this method will be invoked at the end of interceptors chain.
    * It should never be called directly from a custom interceptor.
    *
    * @param ctx invocation context
    * @return arbitrary return value generated by performing this command
    * @throws Throwable in the event of problems.
    */
   Object perform(InvocationContext ctx) throws Throwable;

   /**
    * Used by marshallers to convert this command into an id for streaming.
    *
    * @return the method id of this command.  This is compatible with pre-2.2.0 MethodCall ids.
    */
   byte getCommandId();

   /**
    * Used by marshallers to stream this command across a network
    *
    * @return an object array of arguments, compatible with pre-2.2.0 MethodCall args.
    * @deprecated will be replaced by {@link #writeTo(ObjectOutput)}. Note: don't implement both since they are used
    * during the transition period.
    */
   @Deprecated
   default Object[] getParameters() {
      return Util.EMPTY_OBJECT_ARRAY;
   }

   /**
    * Used by the {@link CommandsFactory} to create a command from raw data read off a stream.
    *
    * @param commandId  command id to set.  This is usually unused but *could* be used in the event of a command having
    *                   multiple IDs, such as {@link org.infinispan.commands.write.PutKeyValueCommand}.
    * @param parameters object array of args
    * @deprecated will be replaced by {@link #readFrom(ObjectInput)}. Note: don't implement both since they are used
    * during the transition period.
    */
   @Deprecated
   default void setParameters(int commandId, Object[] parameters) {
   }

   /**
    * If true, a return value will be provided when performed remotely.  Otherwise, a remote {@link org.infinispan.remoting.responses.ResponseGenerator}
    * may choose to simply return null to save on marshalling costs.
    * @return true or false
    */
   boolean isReturnValueExpected();

   /**
    * If true, the command is processed asynchronously in a thread provided by an Infinispan thread pool. Otherwise,
    * the command is processed directly in the JGroups thread.
    * 
    * This feature allows to avoid keep a JGroups thread busy that can originate discard of messages and
    * retransmissions. So, the commands that can block (waiting for some state, acquiring locks, etc.) should return
    * true.
    *
    * @return  {@code true} if the command can block/wait, {@code false} otherwise
    */
   boolean canBlock();

   /**
    * Writes this instance to the {@link ObjectOutput}.
    *
    * @param output the stream.
    * @throws IOException if an error occurred during the I/O.
    */
   default void writeTo(ObjectOutput output) throws IOException {
      //no-op by default
   }

   /**
    * Reads this instance from the stream written by {@link #writeTo(ObjectOutput)}.
    *
    * @param input the stream to read.
    * @throws IOException            if an error occurred during the I/O.
    * @throws ClassNotFoundException if it tries to load an undefined class.
    */
   default void readFrom(ObjectInput input) throws IOException, ClassNotFoundException {
      //no-op by default
   }
}